| 摘要 |
An optical system for imaging an object on an image acquisition unit includes a first lens unit, a second lens unit, a third lens unit, a fourth lens unit, a fifth lens unit, and a sixth lens unit disposed from the object in the direction of the image acquisition unit. The second lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: Deltathetag<sup2>F</sup2>>0.025. The third lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: Deltathetag<sup2>F</sup2><-0.0015. The fifth lens unit is manufactured from a material whose deviation of the relative partial dispersion fulfills the condition: Deltathetag<sup2>F</sup2><-0.005. According to the disclosed system, the secondary spectrum is reduced and a relative aperture is sufficient so that the optical system is usable in a telescopic sight.
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